With this type of application, it is very possible that 3D could have real impact on commerce and industry far beyond where anyone would have imagined. Its application is evolving and this sector is just young.

Yes you are right. 3-D printing is no longer just for prototypes, but can also be used for limited-run end-user products. For long runs its still cheaper to use stamp dies for sheet metal, injection molds for plastic parts, and CNC (computer numerical control) machine tools for metal parts, but I predict that the day is in sight when even mass produced items will be using cheap, super-fast versions of todays 3-D printers.

Printing is a great way of producing 2-D objects, but not necessarily a quick way of making 3-D ones.

However, if you're making something from tough, notoriously refractory materials, (which is pretty much par for the course when building rocket motors), it makes a lot more sense to build them up than to turn a large lump of the stuff into (mostly) scrap.

I think most of you guys missed the main point. 3D printing allows products to be made in shapes that cannot be done via machining. In order to make complex parts conventionally many pieces have to be assembled. NASA did a rocket motor with 3D printing and claimed it saved over 100 parts. The result can be cheaper, and more robust due to fewer failure points.

We are not missing any point - I think we are in sync here. The impact of 3D is very obvious to this community. The opportunity is so huge that in future manufcturers may focus on selling files as they know you can print the items at home. They get revenue from the sale of the printing files. Say you want to buy a toothbruch, you go online and pay for the file design and print at home.